/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.tsfile.utils;

import java.nio.ByteBuffer;

public class Murmur128Hash {

  /**
   *  get hashcode of value by seed
   * @param value value
   * @param seed seend
   * @return hashcode of value
   */
  public static int hash(String value, int seed){
    return (int) hash3_x64_128(ByteBuffer.wrap(value.getBytes()), 0, value.length(), seed);
  }

  /**************************************
   * Methods to perform murmur 128 hash.
   **************************************/
  private static long getBlock(ByteBuffer key, int offset, int index) {
    int i_8 = index << 3;
    int blockOffset = offset + i_8;
    return ((long) key.get(blockOffset) & 0xff) + (((long) key.get(blockOffset + 1) & 0xff) << 8)
        +
        (((long) key.get(blockOffset + 2) & 0xff) << 16) + (
        ((long) key.get(blockOffset + 3) & 0xff) << 24) +
        (((long) key.get(blockOffset + 4) & 0xff) << 32) + (
        ((long) key.get(blockOffset + 5) & 0xff) << 40) +
        (((long) key.get(blockOffset + 6) & 0xff) << 48) + (
        ((long) key.get(blockOffset + 7) & 0xff) << 56);
  }

  private static long rotl64(long v, int n) {
    return ((v << n) | (v >>> (64 - n)));
  }

  private static long fmix(long k) {
    k ^= k >>> 33;
    k *= 0xff51afd7ed558ccdL;
    k ^= k >>> 33;
    k *= 0xc4ceb9fe1a85ec53L;
    k ^= k >>> 33;
    return k;
  }

  private static long hash3_x64_128(ByteBuffer key, int offset, int length, long seed) {
    final int nblocks = length >> 4; // Process as 128-bit blocks.
    long h1 = seed;
    long h2 = seed;
    long c1 = 0x87c37b91114253d5L;
    long c2 = 0x4cf5ad432745937fL;
    // ----------
    // body
    for (int i = 0; i < nblocks; i++) {
      long k1 = getBlock(key, offset, i * 2 + 0);
      long k2 = getBlock(key, offset, i * 2 + 1);
      k1 *= c1;
      k1 = rotl64(k1, 31);
      k1 *= c2;
      h1 ^= k1;
      h1 = rotl64(h1, 27);
      h1 += h2;
      h1 = h1 * 5 + 0x52dce729;
      k2 *= c2;
      k2 = rotl64(k2, 33);
      k2 *= c1;
      h2 ^= k2;
      h2 = rotl64(h2, 31);
      h2 += h1;
      h2 = h2 * 5 + 0x38495ab5;
    }
    // ----------
    // tail
    // Advance offset to the unprocessed tail of the data.
    offset += nblocks * 16;
    long k1 = 0;
    long k2 = 0;
    switch (length & 15) {
      case 15:
        k2 ^= ((long) key.get(offset + 14)) << 48;
        // fallthrough
      case 14:
        k2 ^= ((long) key.get(offset + 13)) << 40;
        // fallthrough
      case 13:
        k2 ^= ((long) key.get(offset + 12)) << 32;
        // fallthrough
      case 12:
        k2 ^= ((long) key.get(offset + 11)) << 24;
        // fallthrough
      case 11:
        k2 ^= ((long) key.get(offset + 10)) << 16;
        // fallthrough
      case 10:
        k2 ^= ((long) key.get(offset + 9)) << 8;
        // fallthrough
      case 9:
        k2 ^= ((long) key.get(offset + 8));
        k2 *= c2;
        k2 = rotl64(k2, 33);
        k2 *= c1;
        h2 ^= k2;
        // fallthrough
      case 8:
        k1 ^= ((long) key.get(offset + 7)) << 56;
        // fallthrough
      case 7:
        k1 ^= ((long) key.get(offset + 6)) << 48;
        // fallthrough
      case 6:
        k1 ^= ((long) key.get(offset + 5)) << 40;
        // fallthrough
      case 5:
        k1 ^= ((long) key.get(offset + 4)) << 32;
        // fallthrough
      case 4:
        k1 ^= ((long) key.get(offset + 3)) << 24;
        // fallthrough
      case 3:
        k1 ^= ((long) key.get(offset + 2)) << 16;
        // fallthrough
      case 2:
        k1 ^= ((long) key.get(offset + 1)) << 8;
        // fallthrough
      case 1:
        k1 ^= (key.get(offset));
        k1 *= c1;
        k1 = rotl64(k1, 31);
        k1 *= c2;
        h1 ^= k1;
        break;
      default: // 0
        // do nothing

    }
    // ----------
    // finalization
    h1 ^= length;
    h2 ^= length;
    h1 += h2;
    h2 += h1;
    h1 = fmix(h1);
    h2 = fmix(h2);
    h1 += h2;
    h2 += h1;
    return h1 + h2;
  }

}
